1. Field of the Invention
The present invention relates generally to implements for treating freshly cut crops and, more particularly, to crop conditioners for fracturing the stems of the crop to augment drying by permitting escape of fluids from the fractured stems.
2. Discussion of the Prior Art
In U.S. Pat. No. 3,472,003, a crop conditioner is disclosed which includes a first roll rotatable on a fixed axis and a second roll having ends mounted for rotation in plates that are each shiftably mounted through a four-point suspension by a pair of arms pivotally coupled to a frame member and to the plate. A pair of chains extend from the plates and are fastened to opposite ends of a spring disposed beneath the rolls for biasing the upper shiftable roll toward the lower fixed roll.
In the afore-mentioned patent, the crop conditioner is constructed to provide substantially rectilinear movement of the shiftably mounted roll while retaining a substantially uniform pressure between the rolls despite a lack of uniformity in the flow of crop material between the rolls. To this end, the spring employed in the conditioner for biasing the upper roll toward the lower roll is connected to the plates through chains so that as the plates and the upper roll move away from the lower roll, a force builds up due to the stretching of the spring that is transmitted directly to the plates. Thus, the farther apart the rolls are, the larger the biasing force urging the upper roll back toward the lower roll becomes.
In devices such as that disclosed in the afore-mentioned patent, in order to provide a biasing force that is substantially uniform over the range of movement of the upper roll, it is conventional to employ a single large spring having a spring rate of less than 35 pounds per inch and a maximum load of over 1000 pounds. By employing such a construction, the amount of variation in the biasing force of the spring over the range of motion of the upper roll is kept within a reasonable range. However, there is still some increase in spring pressure as the rolls separate.
Several problems have been found to exist in employing a crop conditioner which provides a constant or substantially constant biasing pressure of the upper or movable roll. For example, it is known that during operation of crop conditioners, oversized mats or slugs of crop material are occasionally turned up by the conditioner and pass into the gap between the two rolls. When these slugs enter the gap, they encounter only a portion of the width of the rolls and lift the upper roll from the lower roll against the biasing force so that, along the remaining length of the rolls, no conditioning occurs due to the formation of a gap which is so large relative to the thickness of the crop material passing through the gap that no conditioning occurs.
In addition, because the slugs encounter constant resistance from the upper roll, there is no release of the slug as it enters the gap and the conditioner drive mechanism may slip or stop due to the increased resistance to rotation of the rolls caused by the slug.